Container for the transport and transfer of nanomaterials

ABSTRACT

Aspects of the invention are directed to a container comprising a tub, a basket, and a lid. The tub is adapted to hold a liquid and comprises a bottom and a tub sidewall having an upper rim defining an opening in the tub. The basket is disposed on the bottom of the tub and comprises a base and a basket sidewall. The base defines a perimeter, and the basket sidewall runs along at least a portion of this perimeter. The lid contacts the upper rim and comprises a filler piece. The filler piece occupies a volume inside the tub between the base and a plane defined by the upper rim. The container is adapted to hold a sensitive film stack without damage or degradation to the film stack. The container is further adapted to facilitate the easy transfer of the film stack to a new substrate.

FIELD OF THE INVENTION

The present invention relates generally to containers, and, moreparticularly, to containers for use in handling sensitive materials suchas nanomaterials.

BACKGROUND OF THE INVENTION

Nanomaterials are presently the target of intense study because of theirmany interesting and useful mechanical, optical, and electricalproperties. Graphene, for example, can exhibit very high electron- andhole-mobilities and, as a result, may allow graphene-based electronicdevices to display extremely high switching speeds. Moreover, becausegraphene is planar, it is compatible with many well-developedsemiconductor processing techniques. Graphene may also be used as anelectrode material in energy storage devices, as a membrane material inelectromechanical systems, as a pressure sensor, as a detector forchemical or biological molecules or cells, and in a multiplicity ofother such technical applications.

Presently, high quality and large area graphene can be formed bychemical vapor deposition (CVD). Such CVD processes typically involveexposing a copper foil substrate to hydrogen and methane in a CVD tubefurnace reactor. Once so formed, the graphene can be transferred fromthe copper foil deposition substrate to another substrate for use inwhatever application is of interest. That said, because of the delicatenature of graphene, such a “substrate transfer” process must be handledvery carefully to avoid film damage and degradation. In fact, thetransfer of the graphene from its copper deposition substrate to a newsubstrate is typically a multi-step process. In one methodology, forexample, substrate transfer is initiated by depositing a thin polymercoating on a graphene-copper film stack and then floating the resultingpolymer-graphene-copper film stack on a bath of a liquid copper etchantto remove the copper foil deposition substrate. The resultantpolymer-graphene film stack is then cleaned several times bysequentially floating the film stack on several baths of deionizedwater. After being sufficiently cleaned, a new substrate is immersed ina water bath under the floating polymer-graphene film stack and liftedupward and out of the water bath so as to place the film stack on top ofthe new substrate. The polymer layer is then stripped by rinsing thepolymer-graphene-substrate film stack with an appropriate etchant. Aftersome further cleaning and drying, the desired graphene-substrate filmstack is finally achieved.

Because of the above-described nature of the substrate transfer processfor graphene, a recipient who buys graphene from a graphene manufacturerwith the graphene still on its original copper deposition substrate musthave a certain amount of expertise in wet chemical processing in orderto transfer the received graphene to whatever substrate that recipientwishes to utilize. Many recipients do not have this kind of expertise,nor do they necessarily have the required wet chemical processinginfrastructure. The alternative, that is, for the recipient to send itssubstrate to the graphene manufacturer and have the manufacturer performthe substrate transfer process at the manufacturer's site, is also notparticularly attractive. Shipping substrates back and forth isburdensome and time consuming. Moreover, because of the proprietarynature of many applications, these recipients are not interested inexposing their substrates to inspection offsite.

For the foregoing reasons, there is a need for apparatus that allow ananomaterial such as CVD graphene to be shipped to a recipient sitewithout damage or degradation, and, once at the recipient site,facilitate the recipient in transferring that nanomaterial to whatevernew substrate the recipient desires without requiring that the recipientperform numerous or complex processing steps.

SUMMARY OF THE INVENTION

Embodiments of the present invention address the above-identified needsby providing a container that both serves to protect a film stackcontaining a nanomaterial during transport, and to ease the transfer ofthe nanomaterial in the film stack to a new substrate after thenanomaterial reaches its destination.

Aspects of the invention are directed to a container comprising a tub, abasket, and a lid. The tub is adapted to hold a liquid and comprises abottom and a tub sidewall having an upper rim defining an opening in thetub. The basket, in turn, is disposed on the bottom of the tub andcomprises a base and a basket sidewall. The base defines a perimeter,and the basket sidewall runs along at least a portion of this perimeter.The lid contacts the upper rim and comprises a filler piece. The fillerpiece occupies a volume inside the tub between the base and a planedefined by the upper rim.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 shows a perspective view of a container enclosing a film stack,in accordance with an illustrative embodiment of the invention;

FIG. 2 shows a perspective view of the FIG. 1 container and film stackwith the lid removed;

FIG. 3 shows an exploded perspective view of the FIG. 1 container andfilm stack;

FIG. 4 shows a perspective view the FIG. 1 film stack on the basket ofthe FIG. 1 container;

FIG. 5 shows a sectional view of the FIG. 1 film stack on the basket ofthe FIG. 1 container;

FIG. 6 shows a perspective view of one of the tabs of the basket of theFIG. 1 container;

FIG. 7 shows a perspective view of the lid of the FIG. 1 container;

FIG. 8 shows a sectional view of the lower surface of the lid of theFIG. 1 container;

FIG. 9 shows another exploded perspective view of the FIG. 1 containerand film stack;

FIG. 10 shows a sectional view of the FIG. 1 container and film stackwith the container in its closed state;

FIG. 11 shows a magnified sectional view of a lower corner of the FIG. 1container and film stack with the container in its closed state;

FIG. 12 shows a magnified sectional view of a lower central region ofthe FIG. 1 container and film stack with the container in its closedstate;

FIG. 13 shows a perspective view of the FIG. 1 container and film stackwith the lid, cover sheet, basket, and film stack removed from the tub,and the tub being filled with water;

FIG. 14 shows a partially cutaway perspective view of the FIG. 1 filmstack and the basket of the FIG. 1 container being placed into thewater-filled tub of the FIG. 1 container;

FIG. 15 shows a sectional view of the FIG. 1 film stack rising to floaton water in the tub of the FIG. 1 container;

FIG. 16 shows a magnified sectional view of the FIG. 1 film stackfloating on water in the tub of the FIG. 1 container;

FIG. 17 shows a perspective view of a recipient's substrate beinginserted into the basket of the FIG. 1 container below the floating FIG.1 film stack;

FIG. 18 shows a perspective view of the recipient's substrate resting onthe basket of the FIG. 1 container below the floating FIG. 1 film stack;

FIG. 19 shows a perspective view of the basket of the FIG. 1 containerbeing removed from the tub of the FIG. 1 container such that the FIG. 1film stack becomes positioned onto the recipient's substrate;

FIG. 20 shows a sectional view of the FIG. 1 film stack disposed on therecipient's substrate on the basket of the FIG. 1 container; and

FIG. 21 shows a side elevational view of the FIG. 1 film stack disposedon the recipient's substrate with the protective film being removed byacetone.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described with reference to illustrativeembodiments. For this reason, numerous modifications can be made tothese embodiments and the results will still come within the scope ofthe invention. No limitations with respect to the specific embodimentsdescribed herein are intended or should be inferred.

FIGS. 1-8 show various aspects of a container 100 enclosing ananomaterial-containing film stack 200, in accordance with anillustrative embodiment of the invention. The container 100 can beconceptually separated into four base elements: a tub 105, a basket 110,a cover sheet 115, and a lid 120. When the container 100 is in itsclosed state, these four base elements nest to form a unified structurein which the film stack 200 can be shipped to a remote recipient withoutdamage or degradation. Once at the recipient's site, the container 100is adapted to come apart to form a “kit” that facilitates the recipientin transferring the nanomaterial from the film stack 200 to whatever newsubstrate the recipient desires. The illustrative container 100 therebyserves at least two separate functions: 1) safe transport of the filmstack 200; and 2) eased transfer of the nanomaterial in the film stack200 to a new substrate.

FIG. 1 shows a perspective view of the container 100 and the film stack200 while the container 100 is in its closed state. In addition, FIG. 2shows a perspective view of the container 100 and the film stack 200with the lid 120 removed, and FIG. 3 shows an exploded perspective viewof the container 100 and the film stack 200. In the present illustrativeembodiment, the tub 105 comprises a bottom 125 that is substantiallysquare in shape. A tub sidewall 130 is attached to the bottom 125 andforms a watertight volume therewith, which allows the tub 105 to hold aliquid (e.g., water) without leakage. An upper rim 135 at the top of thetub sidewall 130 defines an opening 140 in the tub 105. The tub 105 ispreferably transparent. The tub 105 may be formed, for example, from atransparent thermoplastic polymer such as polycarbonate, polyvinylchloride, polyamide, polypropylene, and a multiplicity of othermaterials.

The basket 110 is perhaps the most complex element of the container 100because it comes into direct contact with the film stack 200 duringtransport and also serves several functions during the subsequentsubstrate transfer process. In a manner similar to the tub 105, thebasket 110 includes a base 145 that is in the shape of a square.Nevertheless, the base 145 has dimensions (i.e., width and length)somewhat smaller than the bottom 125 of the tub 105 so that the basket110 can rest on the bottom 125 of the tub 105 when the container 100 isin its closed state. A basket sidewall 150 runs along three of the foursides of the base 145, leaving one side of the basket 110 without thesidewall and open. In so doing, the basket sidewall 150 can be describedas running along only a portion of the perimeter of the base 145. Thebasket sidewall 150, moreover, defines a plurality of apertures 155therein. Like the tub 105, the basket sidewall 150 may comprise a clearthermoplastic polymer. The base 145 of the basket 110, in contrast,preferably comprises a fabric comprising, for example, polyester thread.The dissimilar materials of the plastic basket sidewall 150 and thefabric base 145 may be attached to one another by, for example, anadhesive strip (not specifically shown). FIG. 4 shows a perspective viewof the basket 110 and the film stack 200 with the film stack 200 sittingon the base 145 of the basket 110, as it would be during transport. FIG.5 shows a sectional view of the film stack 200 resting in this position.

In addition to the base 145 and the basket sidewall 150, the basket 110also includes two tabs 160. FIG. 6 shows a perspective view of one ofthese two tabs 160. Each of the tabs 160 is rotatably coupled to arespective side of the basket sidewall 150 via a respective screw 165.Each of the tabs 160 is thereby able to be rotated so that it alignswith its respective sidewall portion or projects outward from itsrespective sidewall portion. In this manner, the tabs 160 allow thebasket 110 to be suspended from the upper rim 135 of the tub 105, which,as will be detailed below, is a useful function during substratetransfer.

The cover sheet 115 in the present illustrative embodiment is merely asheet of fabric that acts to protect the upper surface of the film stack200. It may, as a result, be formed of the same material as the base 145of the basket 110 (e.g., a fabric formed of polyester thread).

Lastly, the lid 120 comprises a cover 170 and a filler piece 175, andmay be formed from the same material as the tub 105 (e.g., a transparentthermoplastic polymer). When the container 100 is closed, the cover 170is adapted to contact the upper rim 135 of the tub 105 and thereby actto close the opening 140 in the tub 105. So positioned, the cover 170may be removably fixated to the tub 105 by one of several temporaryfixation means such as a relatively weak adhesive (e.g., rubber cement),elastic straps (e.g., rubber bands), or external wrapping (e.g.,cellophane) (none of which is specifically shown in the figures). Thefiller piece 175 of the lid 120 defines a hollow square block thatprotrudes downward from the cover 170. The filler piece 175 isdimensioned so that, when the tub 105 is closed by the lid 120 with thebasket 110 in place, the filler piece 175 occupies most of the volumeinside the tub 105 between the base 145 of the basket 110 and a plane180 defined by the upper rim 135 of the tub 105 (shown in FIG. 3). Thatis, the filler piece 175 has a width and length slightly smaller thanthe base 145 of the basket 110, while having a height slightly smallerthan the distance between the base 145 and the plane 180. In thisposition, a lower surface 185 of the filler piece 175 faces the bottom125 of the tub 105. FIG. 7 shows a perspective view of the lid 120 alonewith the lower surface 185 clearly visible, while FIG. 8 shows asectional view of the lower surface 185 of the lid 120. In the presentembodiment, the lower surface 185 is not entirely flat but has bevelededges 190 that cause the lower surface 185 to appear somewhat recessedor concave when viewed looking up from the bottom 125 of the tub 105.

The above-described container 100 is suitable for handling manydifferent types of nanomaterials with different morphologies (e.g.,films, particles, rods, pills, cages, fibers, shells). Nevertheless, forpurposes of describing aspects of the invention, the film stack 200 isassumed to comprise one or more layers of graphene 205 coated by aprotective coating 210 of poly(methylmethacrylate) (PMMA), a type oftransparent thermoplastic polymer easily stripped by acetone ((CH₃)₂CO).These constituent members of the film stack 200 are explicitly labeledin the magnified sectional view in FIG. 5. Graphene, as that term isused herein, refers to a planar sheet of sp²-bonded carbon atoms thatare densely packed in a honeycomb crystal lattice. High quality andlarge-area graphene films (both single layer and multi-layer) can besynthesized by CVD on metal substrates such as copper foil. U.S. PatentPublication No. 2011/0091647, to Colombo et al. and entitled “GrapheneSynthesis by Chemical Vapor Deposition,” hereby incorporated byreference herein, for example, teaches the CVD of graphene on metalsubstrates using hydrogen (H₂) and methane (CH₄) in an otherwise largelyconventional CVD tube furnace reactor. A copper foil substrate is loadedinto the CVD tube furnace and hydrogen gas is introduced at a ratebetween 1 to 100 standard cubic centimeters per minute (sccm) whileheating the substrate to a temperature between 400 degrees Celsius (°C.) and 1,400° C. These conditions are maintained for a duration of timebetween 0.1 to 60 minutes. Next methane is introduced into the CVD tubefurnace at a flow rate between 1 to 5,000 sccm at between 10 mTorr to780 Torr of pressure while reducing the flow rate of hydrogen gas toless than 10 sccm. Graphene is synthesized on the copper foil substrateover a period of time between 0.001 to 10 minutes following theintroduction of the methane.

Once synthesized on a copper foil, the one or more layers of graphene205 can be coated by the PMMA protective coating 210 utilizingconventional spray coating or spin coating techniques. The copper foilcan then be selectively removed by floating the polymer-graphene-copperfilm stack with the PMMA facing up on a bath of copper etchantcomprising, for example, ferric chloride (FeCl₃), hydrochloric acid(HCl), and water. With the copper foil removed, the polymer-graphenefilm stack 200 can be washed by floating it on one or more baths ofdeionized water (H₂O).

The resultant film stack 200 (i.e., PMMA-graphene) is then in conditionfor placement in the container 100 and shipment to its intendedlocation. FIGS. 9-12 show various aspects of the container 100 and thefilm stack 200 during such transport. More particularly, FIG. 9 shows anexploded perspective view of the container 100 and the film stack 200,while FIG. 10 shows a sectional view of the container 100 and the filmstack 200 with the container 100 in its closed state. In addition, FIGS.11 and 12 show magnified sectional views of a lower corner region and alower central region, respectively, of the film stack 200 and thecontainer 100 in its closed state. In preparation for transport, thefilm stack 200 is first placed on the base 145 of the basket 110 withthe PMMA protective coating 210 facing up, and the basket 110 is thenplaced on the bottom 125 of the tub 105. The cover sheet 115 is thenplaced on the film stack 200 and the base 145, and finally, the lid 120is removably attached to the upper rim 135 of the tub 105 so as to closethe container 100. Configured in this manner, the filler piece 175 ofthe lid 120 presses down on the cover sheet 115 which, in turn, pressesthe base 145 of the basket 110 against the bottom 125 of the tub 105. Atthe same time, the film stack 200 is firmly sandwiched between the coversheet 115 and the base 145 of the basket 110, where it is held immobile.Advantageously, the slightly recessed shape of the lower surface 185 ofthe filler piece 175 causes the filler piece 175 to place more of itspressing force on the peripheries of the cover sheet 115 and the base145 of the basket 110, while placing less pressure on the center of thecover sheet 115 and the base 145 where the film stack 200 is located.Although the film stack 200 is still firmly held in place, the chance ofmechanical damage to the film stack 200 caused by its enclosure in thecontainer 100 is thereby reduced.

Once safely received by the recipient, the container 100 is then able toserve its second function, that is, to serve as a kit for the easytransfer of the enclosed film stack 200 to a substrate of therecipient's choosing (hereinafter, the “recipient's substrate” 300).FIGS. 13-21 go on to show aspects of various intermediate steps of thistransfer process. In describing this processing, the film stack 200continues to be assumed for illustrative purposes to be the graphene 205coated with the PMMA protective coating 210. The graphene 205 faces thebase 145 of the basket 110, and the PMMA protective coating 210 facesupward.

The initial step of the substrate transfer process has the recipientremove the lid 120 from the tub 105, and, with the lid 120 no longer inplace, remove the cover sheet 115 and the basket 110 from the tub 105.The recipient is then instructed to deploy the two tabs 160 on thebasket 110 so that the tabs 160 extend outward from the basket sidewall150. The recipient is further instructed to fill the tub 105 withdeionized water 195. The performance of these steps is shown by theperspective view of FIG. 13.

Next, the recipient is instructed to suspend the basket 110 from theupper rim 135 of the tub 105 (using the deployed tabs 160), as shown inin the partially cutaway perspective view in FIG. 14. This, in turn,causes the PMMA-graphene film stack 200 to float off of the base 145 ofthe basket 110 to the surface of the water 195. Such a condition isshown in FIGS. 15 and 16, where FIG. 15 shows a sectional view of thefilm stack 200 rising to float on the water 195 of the tub 105, and FIG.16 shows a magnified sectional view of the film stack 200 floating onthe water 195 in the tub 105.

The recipient is then further instructed to place the recipient'ssubstrate 300 into the basket 110 so that the recipient's substrate 300,which does not float, ultimately falls onto the base 145 of the basket110 below the floating PMMA-graphene film stack 200. This insertion isfacilitated by the “missing” sidewall portion of the basket 110. FIG. 17shows a perspective view of the insertion of the recipient's substrate300 into the basket 110 below the floating film stack 200. FIG. 18, inturn, shows a perspective view of the recipient's substrate 300positioned in the basket 110 below the floating film stack 200.

With the recipient's substrate 300 positioned in the basket 110 belowthe floating PMMA-graphene film stack 200, the recipient is theninstructed to lift the basket 110 from the tub 105 so that the filmstack 200 becomes positioned onto the recipient's substrate 300. Ventingof the water 195 while the basket 110 is being lifted from the tub 105is facilitated by the apertures 155 in the basket sidewall 150. Theraising of the basket 110 in this manner is illustrated in theperspective view in FIG. 19. The resultant placement of the film stack200 on the recipient's substrate 300 is shown in the sectional view inFIG. 20.

Finally, the recipient is instructed to remove the recipient's substrate300 (on which is deposited the PMMA-graphene film stack 200) from thebasket 110 and to strip off the PMMA protective coating 210 with anappropriate solvent. PMMA is, for example, readily removed by acetone.FIG. 21 shows a side elevational view of this processing step. In sodoing, the substrate transfer is completed and the recipient is leftwith the bare graphene 205 on the recipient's substrate 300.

In this manner, the container 100, when combined with an appropriatelyconfigured nanomaterial-containing film stack like the film stack 200,serves dual functions. When in its closed state, the container 100 formsa unified structure in which a sensitive film stack can be shippedwithout degradation or damage. Once at the recipient's site, thecontainer 100 comes apart to form a kit that facilitates the recipientin transferring the nanomaterial to whatever new substrate the recipientdesires. The recipient needs have no special expertise in the transferprocessing but, instead, needs only follow simple instructions andutilize readily available chemicals such as deionized water and acetone.There is no need for the recipient to send its substrate to the graphenemanufacturer's site. Shipping times are saved and, perhaps moreimportantly, the recipient's often-proprietary substrate is not open toinspection offsite.

In closing, it should again be emphasized that the above-describedembodiments of the invention are intended to be illustrative only. Otherembodiments can use different types and arrangements of elements forimplementing the described functionality. As just one example, while theparticular embodiment of the container described above has a largelysquare footprint, this shape is merely illustrative and any othersuitable shape (e.g., rectangular, circular, elliptical, hexagonal,etc.) would also fall within the scope of the invention. In such amanner, a container in accordance with aspects of the invention mayeasily be adapted to accommodate different film stack shapes andrecipient substrate shapes. These numerous alternative embodimentswithin the scope of the appended claims will be apparent to one skilledin the art.

Moreover, all the features disclosed herein may be replaced byalternative features serving the same, equivalent, or similar purposes,unless expressly stated otherwise. Thus, unless expressly statedotherwise, each feature disclosed is one example only of a genericseries of equivalent or similar features.

What is claimed is:
 1. A container comprising: (a) a tub, the tubadapted to hold a liquid and comprising a bottom and a tub sidewallhaving an upper rim defining an opening in the tub; (b) a basket, thebasket disposed on the bottom and comprising: (i) a base, the basedefining a perimeter; and (ii) a basket sidewall, the basket sidewallrunning along at least a portion of the perimeter; and (c) a lid, thelid contacting the upper rim and comprising a filler piece, the fillerpiece occupying a volume inside the tub between the base and a planedefined by the upper rim.
 2. The container of claim 1, wherein the basecomprises a fabric.
 3. The container of claim 1, wherein the lid coversthe opening in the tub.
 4. The container of claim 1, wherein the fillerpiece defines a lower surface, the lower surface disposed inside the tuband facing the bottom.
 5. The container of claim 4, wherein the lowersurface defines a beveled edge.
 6. The container of claim 1, wherein thebasket sidewall runs along only a portion of the perimeter.
 7. Thecontainer of claim 1, where the base describes four edges and the basketsidewall runs along only three of the four edges.
 8. The container ofclaim 1, wherein the basket sidewall defines an aperture therein.
 9. Thecontainer of claim 1, wherein the basket is adapted such that it can besuspended in the tub from the tub sidewall.
 10. The container of claim1, wherein the basket further comprises a tab, the tab adapted to bepositioned such that it extends outwardly from the basket sidewall. 11.The container of claim 1, wherein the container encloses a film stack,the film stack disposed between the base and the filler piece.
 12. Thecontainer of claim 11, wherein the film stack comprises a nanomaterial.13. The container of claim 12, wherein the nanomaterial comprisesgraphene.
 14. The container of claim 12, wherein the nanomaterial is atleast partially covered by a polymer coating.
 15. The container of claim14, wherein the polymer coating is operative to be stripped by acetone.16. The container of claim 14, wherein the polymer coating comprisespoly(methyl methacrylate).
 17. The container of claim 11, wherein thefilm stack floats when placed in the liquid.
 18. The container of claim11, further comprising a cover sheet, the cover sheet disposed betweenthe film stack and the filler piece.
 19. The container of claim 18,wherein the cover sheet comprises a fabric.
 20. The container of claim11, wherein the film stack is substantially held immobile against thebase.